1. Field of the Invention
The present invention relates to gas and fluid flow conduits such as ductwork, and more particularly to a connector for joining end portions of conduit sections. The connector includes carbon fibers which dissipate and neutralize built-up electrostatic charges resulting from triboelectric processes as vapors, gases or liquids flow through a conduit. Such dissipation and neutralization by use of electrically conductive materials is referred to herein as xe2x80x9cself-grounding.xe2x80x9d
2. Description of the Related Art
Published application Ser. No. 2002/0017333 A1 (xe2x80x9c""333xe2x80x9d), which is incorporated in its entirety herein by reference, discloses a self-grounding dual-wall duct for transporting corrosive vapors and gases, and a process for fabricating such ducts and pipe. The duct has a laminated inner wall whose innermost layer incorporates continuous, helically-wound carbon filament ribbons which dissipate and neutralize built-up electrostatic charges resulting from vapor or gas flow. The ""333 reference further discloses a joint assembly providing high electrical conductivity, and thereby self-grounding, across the joint. The assembly includes a self-grounding collar for joining two dual-laminate duct sections. The collar has a laminate construction including two relatively thin inner layers of carbon filament ribbon impregnated with an epoxy or any other type of chemically resistant vinyl ester resin-and-curing agent admixture, and a relatively thick outer layer of glass filament ribbon impregnated with the admixture. The assembly further includes a sealant having chopped carbonized carbon fibers. The filament layers provide self-grounding of the collar inner surface, and the fibers provide self-grounding of the collar outer surface.
Pat. No. 6,315,004 (xe2x80x9c""004xe2x80x9d) to R. L. Wellman et al., which is incorporated in its entirety herein by reference, discloses a laminated inner wall of a dual-wall fume duct for transporting corrosive vapors and gases, and a process for fabricating the wall. The innermost layer of the wall is made of a cured epoxy or any other type of chemically resistant vinyl ester resin incorporating chopped carbonized carbon fibers.
It is a primary object of the present invention to provide an improved connector impermeable to hazardous gases, vapors and fluids, and which dissipates and neutralizes electrostatic charge build-up on its inner and outer surfaces.
Another object of the invention is to provide a self-grounding connector fabricated using a substantially automated production process amenable to standardization and high quality control.
Yet another object of the invention is to provide a simplified production process using fewer types and lesser amounts of fabrication materials per unit connector.
Other objects of the invention will become evident when the following description is considered with the accompanying drawing figures. In the figures and description, numerals indicate the various features of the invention, like numerals referring to like features throughout both the drawings and description.
These and other objects are achieved by the present invention which in a first aspect provides a rigid self-grounding connector for joining end portions of fluid flow conduit sections. The connector includes an inner layer determining a connector inner surface and including a first highly electrically conductive material, and an outer layer determining a connector outer surface and including a second highly electrically conductive material. These materials, respectively, dissipate and neutralize electrostatic charges accumulating on the inner and outer surfaces.
In another aspect the invention provides a process for making a self-grounding connector for joining end portions of fluid flow conduit sections. The steps include: (a) covering a mandrel with a non-sticking material; (b) forming over the material a layer using a conductive material and a fluidic admixture; (c) forming over the layer a second layer using a second conductive material and the admixture; and (d) removing the formed layers from the mandrel to form the connector.
In yet another aspect the invention provides a first process for making a self-grounding connector for joining end portions of fluid flow conduit sections. The process steps include: (a) forming a fluidic admixture of a settable chemically resistant resin and a curing agent; (b) coating a non-sticking sheeting covering a mandrel with a layer of the admixture; (c) helically winding around the sheeting a band formed by contiguous, continuous electrically conductive ribbons having continuous carbon filaments impregnated with the admixture, thereby forming a ribbon-layer embedded in the admixture layer; (d) coating the ribbon-layer with a second admixture layer; (e) helically winding a layer of surfacing veil wetted out with the admixture; (f) coating the veil with a third admixture layer; (g) depositing chopped carbon fibers to cover the veil; (h) integrating the fibers and admixture to form a layer of wetted out fibers terminating in a smooth outer surface; and (i) orthogonally winding a second band having at least one ribbon impregnated with the admixture, thereby forming a circumferential bead.
In still another aspect the invention provides a second process for making a self-grounding connector for joining end portions of fluid flow conduit sections. The process steps include: (a) forming a fluidic admixture of a settable chemically resistant resin and a curing agent; (b) coating a non-sticking sheeting covering a mandrel with a first layer of the admixture; (c) helically winding around the sheeting a layer of carbon cloth wetted out with the admixture; (d) curing the admixture layer and wetted out cloth; (e) covering the cloth with a layer of putty; (f) helically winding into the putty a layer of surfacing veil; (g) curing the putty; (h) coating the veil with a second layer of the admixture; (i) depositing chopped carbon fibers to cover the veil; (j) integrating the fibers and admixture to form a layer of wetted out fibers terminating in a smooth outer surface; and (k) orthogonally winding a second band having at least one ribbon impregnated with the admixture, thereby forming a circumferential bead.
A more complete understanding of the present invention and other objects, aspects and advantages thereof will be gained from a consideration of the following description of the preferred embodiments read in conjunction with the accompanying drawings provided herein.